The present invention relates to a natural circulation reactor and, more particularly, to a natural circulation reactor suitable for maintaining a reactor core submerged under coolant even on the supposition of breakage of any pipe connected to a pressure vessel of the reactor.
As described in "Annual Meeting of 1987", Japanese Nuclear Society, Corp., (at Nagoya University, Apr. 1-3, 1987), E44, Conceptual Study of Natural Circulation BWR - (1) Plant Outline, a conventional natural circulation reactor has been designed to inject light water from a tank of an accumulated coolant injection system on the supposition of breakage of any pipe connected to a pressure vessel of the reactor.